The 27-year-old forward was substituted during the weekend defeat at Sheffield Wednesday with a hamstring strain in his right leg and is undergoing tests to assess the extent of the injury.
The Magpies top scorer had only returned to action at the beginning of last month after suffering a similar injury back in January which kept him out for four matches.
He returned to action, only to suffer a relapse and miss a further two games before the 2-1 defeat at Hillsborough being his seventh straight appearance for the Toon Army.
However, the fear on Tyneside is the forward may have made his last outing for the club this campaign as Rafa Benitez's side aim for Premier League promotion.
Should tests show Gayle is out for the final five games of the season, Newcastle will have to choose between Daryl Murphy or Aleksandar Mitrovic as their main man in attack.